The present technology relates to a plug for an electrical plug-and-socket connection generally used for the electrical interconnection of a tow vehicle or truck and a trailer. Typically, trailers are equipped with cylindrical formed plugs having a central contact terminal surrounded by a number of perimeter contact terminals. A well-known standard for such a plug and the corresponding socket is the SAE J560 describing a seven pole plug and socket connection. The contact terminals of the plug are wired to the electrical circuit of the trailer and in particular connected to the breaks, turn signals, running signals, and break signals of the trailer. For connecting the trailer to the electrical circuit of the tow vehicle, a socket for connection with the before described plug is mounted at the rear end of the tow vehicle which is suited for matching the contact terminals.
A socket according to another standard is known from U.S. Pat. No. 7,828,708 B2 describing a socket with a housing, a plug-in opening for mounting a plug, and a contact support insert positioned inside the housing. The contact support insert includes contacts extending into the plug-in opening which, however, are designed as flat contacts with an elastically bent contact surface. In order to provide a sealed socket the housing and the contact support insert are comprised of the same material as a single component produced in two consecutive injection molding steps. The rear end of the contacts might be contacted by a suited plug connected to wires leading to the electrical circuit of the tow vehicle. However, the rear end of the socket for connection with the wires to the electrical circuit of the tow vehicle is not sealed and the plug for connecting to the rear end of the contacts cannot be safely secured to a housing of the socket.
In the WO 2012/019625 A1 a socket is disclosed having a hold-closed mechanism that increases the holding force of the cover in the closed position in order to enhance the sealing properties of the hinge-mounted cover of the socket housing. However, the sealing of the contact area of the contacts inserted into the contact insert is not addressed. Further, the rear connection of these contacts is not sealed and specifically secured so that moisture can ingress the contact area of the rear contacts for connection with the electrical circuit of the tow vehicle. Further, the plug for connecting a socket with the electrical circuit of the tow vehicle is not additionally secured to the socket. This might lead to a drop-off of this plug from the socket due to e.g. vibration of the vehicles in use.
The EP 2 535 985 A1 discloses a socket for another plug-and-socket connection according to another (European) standard for the electrical connection of a trailer to a tow vehicle. In this embodiment, the contact insert and the socket housing are injection molded as an integral part with the contacts included into the contact insert. For connecting the contacts in the contact insert to the wires of the harness of the tow vehicle, receptacle contacts connected with wires leading to the electrical circuit of the tow vehicle are inserted into respective openings of the contact insert for contacting the rear side of the contacts provided in the contact insert. The wires are sealed by wire seals surrounding the wire and sealing the wire against the inner surface of the respective opening of the contact insert. However, each of the receptacle contacts have to be inserted individually into the contact insert which is cumbersome and error-prone. Another known alternative stipulates to provide a harness assembly directly and fixed connected with the socket to be mounted in the vehicle. However, the handling of such an integral assembly is difficult. Further, if the socket is mechanically damaged, the change of the socket is laborious and costly because the complete harness including the socket has to be dismounted and newly assembled.
For pulling out a plug inserted into such a socket it is necessary to lift the cover of the socket overlying on the plug body with one hand and to pull the plug off the socket with the other hand. This is cumbersome.